1. Field of the Invention
This invention relates to an optical apparatus and an image displaying apparatus in which the optical apparatus is incorporated.
2. Description of the Related Art
A virtual image displaying apparatus as an image displaying apparatus wherein a virtual image optical system allows a two-dimensional image formed by an image formation apparatus to be observed as an enlarged virtual image by an observer is well known, for example, from JP-T-2005-521099 and Japanese Patent Laid-Open No. 2006-162767.
As conceptually illustrated in FIG. 25, the image displaying apparatus 900 mentioned includes an image formation apparatus 911 including a plurality of pixels arranged in a two-dimensional matrix, a collimate optical system 912 for converting light emitted from the pixels of the image formation apparatus 911 into parallel light and a light conduction section 930 for receiving, conducting and emitting the parallel light from the collimate optical system 912. The light conduction section 930 includes a light conduction plate 931 for propagating incident light in the inside thereof by total reflection and then emitting the propagated light therefrom, a first deflection section 940 formed, for example, from a single-layer light reflecting film for reflecting the light incident to the light conduction plate 931 such that the light incident to the light conduction plate 931 is totally reflected in the inside of the light conduction plate 931 and a second deflection section 950 formed, for example, from a light reflecting multi-layer film having a multi-layer lamination structure for emitting the light propagated in the inside of the light conduction plate 931 by total reflection from the light conduction plate 931. If, for example, a head-mounted display (HMD) unit is formed from such an image displaying apparatus 900 as described above, then reduction in weight and size of the apparatus can be achieved.
Alternatively, a virtual image displaying apparatus as an image displaying apparatus in which a hologram diffraction grating is used in order to allow an observer to observe a two-dimensional image formed by an image formation apparatus as an enlarged virtual image by a virtual image optical system is known, for example, from Japanese Patent Laid-Open No. 2007-094175 and Japanese Patent Laid-Open No. 2007-012530.
As conceptually illustrated in FIGS. 26 and 27, the image displaying apparatus 1000 mentioned above includes, as basic components thereof, an image formation apparatus 1011 for displaying an image, a collimate optical system 1012 and a virtual image optical system or light conduction section 1030 which receives light displayed by the image formation apparatus 1011 and conducts the inputted light to the pupil 41 of an observer. The light conduction section 1030 includes a light conduction plate 1031, and a first diffraction grating member 1040 and a second diffraction grating member 1050 provided on the light conduction plate 1031 and individually formed from a reflection type volume hologram diffraction grating. Light emitted from pixels of the image formation apparatus 1011 is inputted to the collimate optical system 1012, and parallel light is produced by the collimate optical system 1012 and then is introduced to the light conduction plate 1031. The parallel light enters and outgoes from a first face 1032 of the light conduction plate 1031. Meanwhile, the first diffraction grating member 1040 and the second diffraction grating member 1050 are mounted on a second face 1033 of the light conduction plate 1031 which extends in parallel to the first face 1032 of the light conduction plate 1031.